Pile driving mandrel



Nov. 8, 1966 F. RUSCHE FILE DRIVING MANDREL 5 Sheets-Sheet 2 Filed Nov. 15, 1963 INVENTOR FR EDRlC RUSCHE ATTORN EY Nov. 8, 1966 F. RUSCHE PILE DRIVING MANDREL 5 Sheets-Sheet 5 Filed Nov. 15, 1963 INVENTOR. FREDRIC RUSCHE ATTORNEY Nov. 8, 1966 F. RUSCHE 3,283,519

PILE DRIVING MANDREL Filed Nov. 15, 1965 5 Sheets-Sheet 4 FIG. 9

INVENTOR. FREDRIC RUSCHE BYa N.

ATTONEY Nov. 8, 1966 Filed NOV. 15, 1963 COMPRESSIVE LOAD IN LBS.

5 Sheets-Sheet 5 FIG. IO

PRESET COMPRESSION IN HEAD PACKING INIVENTOR. FREDRIC RUSCHE r0000 e700 8000 e000 0 I/l6 I/8 3/l6 l4 5/I6 3/8 7/16 |2 COMPRESSION OF TOP PACKING IN INCHES ATTORNEY United States Patent 3,283,519 PILE DRIVING MANDREL Fredric Rusche, Southfield, Mich. (8125 Medina St., Detroit, Mich.) Filed Nov. 15, 1963, Ser. No. 323,943 20 Claims. (Cl. 6153.72)

This invention relates to pile driving mandrels of the type disclosed in my US Patent 3,006,152 issued October 31, 1961, the disclosure of which is incorporated herein by reference.

In driving piles it is customary to pour a concrete pile into a thin steel casing previously sunk into the ground. The piles may be as much as eighty feet long. The casings are usually made of thin steel, for example of 16 gauge. The casing must be supported while it is being driven, by a mandrel which can be removed after the casing is driven. The casings may be corrugated spirally as known in the art and as shown for example in the U.S. patent to McKee, 2,928,252. The mandrel is connected to the casing by driving connections or lugs which are expressible from the mandrel into contact with the corrugations of the casing, and are withdrawn into the mandrel when the mandrel is to be withdrawn from the casing.

It is of advantage to drive such casings with a solid core mandrel, by which I mean a mandrel, the driving member of which is a circumferentially integral or complete tube which is not split nor made in longitudinal sections. Such solid core mandrels, as disclosed for example in my patent referred to, have been very successful in driving casings, but various problems have been encountered which the present invention is intended to solve.

In mandrels of this type it has been customary to transmit the great force of the driving hammer to thethin shell through plugs which are movable radially in openings through the wall of the tubular core to selectively engage or release the corrugations of the shell. The plugs are arranged in rows extending nearly the length of the tube. Expansible fluid pressure chambers formed by hoses or bladders filled with air under pressure are used to express the plugs into contact with the shells and springs are used to retract the plugs when the air pressure is exhausted.

While mandrels as disclosed in my patent referred to are successful in transmitting great driving forces to the shell, problems arise in connection with the apparatus needed to express and retract the plugs. The mandrels may be as much as sixty feet long and are not less than ten feet long. Any hose or bladder which expresses such a long row of plugs must be supported throughout its length. As heretofore constructed the plugs in a single row are mounted on a rail formed as a single steel channel member running most of the length of the mandrel. This channel member is pushed radially outward by a hose running the length of the mandrel and filled with air under pressure. This arrangement requires four long hoses and requires them to be supported throughout most of the length of the channel members so that they will accurately contact the channel members when they are inflated. This has required an elaborate, heavy and extensive steel structure, known as guts, which is placed inside the mandrel tube and runs its entire length. Because of the relatively small inside diameter of the mandrel, which may be as little as eight and one-half inches, the structure or guts supporting the hose must necessarily be very long and slender and consequently will unavoidably be both laterally and torsionally flexible, regardless of the material of which it is made, usually cold rolled steel. I

Because of the length of the mandrel it is impractical to fasten the guts to the mandrel tube. It could be welded for a short distance at each end, but such a fastening is inadequate both because it is apt to break under 3,283,519- Patented Nov. 8, 1966 impact of the driving hammer and because it leaves a long length of flexible guts between the end fastenings. Consequently as a practical matter the guts have "been left floating, that is they have been entirely detached from the inside of the mandrel tube. In spite of efforts to stiffen the structure of the guts by making weldments of complicated cross section, as shown for example in my patent referred to, it has been impossible to provide guts which are free from the inherent disadvantage of a long slender, flexible structure of considerable inerita, detached from the inside of a mandrel core, which core is subject to high impact forces and to very great acceleration.

When the hammer strikes the core, the core may move downward with great acceleration. The guts tends to maintain its position in space due to its inherent inerita. This causes the guts to bend and to vibrate violently between the end plates of the tube. While the movement between the mandrel core and guts is dimensionally small, it is impossible to prevent all movement due to necessary clearances in manufacturing the mandrels and due to bending and to twisting. The twisting is caused by the spiral corrugations of the shell. As the spiral shell is driven into the earth it sometimes tends to screw itself into the earth and this produces a torque tending to rotate the entire mandrel. The inertia of the guts tends to prevent rotation of the guts and this tends to cause misalignment between the hoses and the channels which support the driving plugs. Consequently torque means is provided to restrict relative rotation between the mandrel tube and the guts. However such torque means can be placed only at each end of the mandrel, and in the case of a very long mandrel, such as sixty feet, this leaves a long length of guts between the torque means which is free to twist under the screwing action of the shell. Either twisting or bending shortens the guts and provides additional clearance at each end, which encourages vibration. All of this produces hammering and impacts between the ends of the guts and the end plates of the mandrel and produces torsional vibrations in the guts itself. This breaks or wears out hoses and breaks the air connections to the hoses.

I have discovered that many of the problems resulting from floating guts can be eliminated or importantly reduced by supporting the guts axially or endwise between a resilient driving means of the proper characteristics and a resilient retarding means of proper characteristics. The driving means is placed at the top of the guts and the retarding means at the bottom, so that the guts is resiliently suspended between the end plates of the tube.

Accordingly it is among the objects of the invention to provide an improved mandrel in which direct contact and impact between the end of the guts and the ends of the mandrel is eliminated, to provide a mandrel structure in which lateral bending and twisting of the guts is materially reduced or eliminated, and to provide an improved mandrel in which the forces due to any vibrations caused by lateral bending or twisting are absorbed before they reach the structure of the mandrel core.

More particularly it is among the objects of the invention to provide an improved mandrel assembly in which the guts is resiliently suspended axially between the ends of the mandrel, and damped to provide improved elastic suspension means for suspending it.

More particularly it is an object of the invention to provide improved damped elastic pads, used as a resilient driving means and as a resilient retarding means between the guts and the mandrel tube.

These and other objects of the invention will be evident from the following description and from the accompanying drawings, in which FIG. 1 is a portion of a mandrel embodying one form upper mandrel which can be used alone.

Such rail may be of C-section.

3 of the invention, shown partly in elevation, partly in section, and partly broken away.

FIG. 2 is a section on the line 22 of FIG. 1 looking in the direction of the arrows.

FIG. 3 is an exploded perspective view of a portion of the mandrel shown in FIG. 1 but showing an asembly of a different form of resilient driving pad.

FIG. 4 is a section on the line 44 of FIG. 1.

FIG. 5 is a section on the line 55 of FIG. 1.

FIG. 6 is a diagrammatic illustration of a coupling and fluid pressure connecting mechanism for two mandrels joined end to end to make a longer mandrel.

FIG. 7 is an exploded perspective view of the lower end of the mandrel shown in FIG. 1, but having a specifically different form of retarding pad.

FIG. 8 is a view partly in section and partly broken away of the lower end of the mandrel shown in FIG. 1, joined to a specifically different form of mandrel, which serves as the lower or bottom section of a long mandrel assembly.

FIG. 9 is an enlarged section of one form of resilient disc forming part of the driving pad shown in FIG. 3; and

.have corresponding elements differing in details of construction. In referring to the two mandrels reference characters below 100 designate elements of a single or Reference characters between 101 and 200 refer to parts corresponding to those similarly numbered in .the 0-100 series.

' Reference characters above 200 refer to parts required to couple the mandrels, but not previously deescribed in the first or upper mandrel.

Referring to FIG. 1 of the drawings, an elongated, circumferentially intact mandrel tube 10 has a driving plate or head plate 12 bolted to its upper end, a foot plate 14 secured to its lower end. The head plate receives the impact of the driving hammer and transmits all driving force to the mandrel. The foot plate transmits this force to somethiing beyond the mandrel whch may be another mandrel, or may be the earth. In the form of the invention shown in FIG. 1 the foot plate 14 is welded to the lower end of the tube 10 and transmits the entire driving force to a coupling tube or sleeve 16 which is welded'to tube 10 and forms a prolongation of it. The

coupling tube 16 may be closed at its lower end by another foot plate 14 which forms the surface which punches the hole in the earth. Alternatively the foot plate 14' may be removed to give access to the inside of the sleeve 16, into which a coupler 18 (FIG. 8) can be inserted for joining a pair of mandrels, as will be explained.

The tube 10 has four rows of elongated openings or slots 20 (see FIGS. 1 and 2) in which are placed radially movable plugs 22 provided on their outer surfaces with slanting lugs 24 matching the spiral corrugations in the surrounding shell (not shown) which the mandrel drives. Each row of slots 20 extends to a point near the ends of the tube. There may be slots at intervals of approximately four feet.

All of the plugs 22 in a single row are attached to an elongated rail 26 as shown in my patent referred to. It extends at least the length of the row of plugs 22, and may extend the entire length of the tube 10. Each plug is attached to the rail in any suitable manner, for example by bolts 28 which are threaded into nylon nuts 30 which can he slid into the C- sections at openings 32 (FIG. 1) and are supported under overhanging edges 34 of the C-sections (FIG. 2). The rails are urged inwardly to retract the plugs out of contact with the shell by a suitable number of springs 36 distributed along the rail, and each seated between a spring seat 38 formed in the rail and a plug 40 threaded in an opening through the wall of the tube. The springs can be inserted through these openings to be assembled with the rails.

As shown best in FIG. 2 the rails 26 and plugs 22 are urged outward against the force of the springs 36 by inflatable hoses or bladders 42 which run substantially the entire length of each row of plugs. A reaEtion support for the four hoses is provided 'by a square tube 44 which runs the length of the tube 10. In order to maintain the square tube centered and to support the hoses in proper relationship to the rails 26, the square :tube 44 is welded to four angle irons 46 which run substantially the entire length of the tube 10. The square tube and the four angle irons form a weldment which constitutes the guts referred to. Near the upper end of the guts, as shown in FIG. 1, a manifold 48 is provided to which air under pressure is conducted by a fittiing 50 whch can be connected to any suitable supply pipe or tube from outside of the tube 10 (FIGS. 1 and 5).

The manifold 48 has four hose connections 62 (FIGS. 1 and 5) to each of which a hose 42 is attached by hose clamps 54. The lower end of each hose is closed by being pinched together, cemented and having all four hoses secured by clamps 55 against a round tube 56 forming the lower end of the square tube 44 (see FIGS. 6 and 8). Each hose forms a closed air pressure chamber which can be supplied by pressure fluid through the fitting 50 and when so supplied all of the hoses expand to force the rails 26 radially outward against the springs 36 and express the lugs 24 into engagement with the corrugations of the shell.

It would :be desirable, if it could be done, to have the guts fit tightly within the inside of the tube 10.. But the long weldment must be inserted from one end of the tube 10, which may be as much as sixty feet long. Clearance must be provided between the edges of the angle irons 46 and the inside wall of the tube as indicated in FIG. 2. This unavoidably permits seemingly slight lateral bending or whip of the guts under impact of the driving hammer, but even this slight movement causes serious and even destructive vibration. The clearance leaves the guts free for torsional deflection due to the screwing action of the spirally corrugated shell as the assembly is being driveninto the earth. Partly due to this necessary lateral clearance, and partly due to the necessity for other manufacturing tolerances, it is impractical to make a weldment whose length is exactly equal to the distance between the head plates and the foot plates. Moreover it is undesirable to have the ends of the guts in actual contact with the head and foot plates.

Accordingly it is a feature of my invention to provide a resilient or elastic driving element between the head plate and the guts and a similar retarding element between the foot plate and the guts. Some advantages of the invention can be realized by using only the resilient driving element, or only the retarding element, but I prefer to use both. The driving element may be a single thick, resilient pad 60, as shown in FIG. 1, but I prefer to-use a stack of thinner discs or pads as shown in FIG. 3, for

these facilitate preloa-ding. The top and bottom discs of the stack, as well as a number of intermediate discs 62, are relatively thick, for example /2 inch, while the remaining discs are relatively thin, for example A to inch. Some of the thin discs 64 are plain, while others 66 are corrugated. The single pad, or each plain disc, may be a laminated stack of layers of textile fabric or other fibrous material such as about 30 layers of woven fabric for a /2 inch disc. These layers are impregnated and bonded together in a suitable volume of suitable elastomer such as cured natural or synthetic rubber of the desired durometer to provide a highly damped elastic pad. This pad is deformed slightly axially of the tube by the tremendous forces of the driving hammer, and

recovers elastically from this deformation. The deflection is highly damped so that it does not set up objectionable vibrations in the pad itself nor in the guts.

Consequently the pad is capable of absorbing very high axial forces.

The corrugated pads 66 are preferably constructed as shown in FIG. 9. A number of relatively thin layers of fabric, for example about four, are stacked to form an inner layer or core 70 which is impregnated and bonded as described above. This core is sandwiched between two outer, somewhat thicker layers 72 and 74. The entire stack is bonded together. In addition the layer 74 and the adjacent part of the core 70 are corrugated as shown in FIG. 9 by any suitable press as the disc is being bonded. The corrugations provide parallel damped springs which are deformable under the impact of the driving hammer. As shown in FIG. 3 each corrugated disc is placed between a pair of plain discs and alternate corrugated discs are placed with the corrugations transverse, and preferably at right angles to one another.

The upper end of each rod or angle iron 46 in the weldment forming the guts is welded to a flat radially extending plate 80 (FIGS. 1 and 3). The square tube 44 extends through and beyond this plate and is welded to it. The end plate or top plate 12 has a larger square tube 82 welded to its lower face as shown in FIGS. 1 and 3. When the mandrel is assembled the upper end of the square tube 44 telescopes into the square tube 82 to prevent relative rotation of the guts and the tube as far as this is possible within the requirements of clearance and manufacturing tolerances. This reduces torsional vibration of the guts to the screwing action of the shell under impact of the driving hammer. The discs 62, 64, 66 are each centrally perforated by a square hole to receive the square tubes 44 and 84.

As shown particularly in FIGS. 1 and 7, at the lower end of the guts a bottom or end plate 84, similar to the top end plat-e 80, is welded to the angle irons 46 and to the rounded end 56 of the square tube 44. A retarding pad 86 generally similar to the driving pad 60 is placed between the end plate 84 and the foot plate 14, which latter plate has welded to it a number of axially extending dowels or studs 88 which may bear against wear pieces or short angle irons 89 (FIG. 2) which are welded to the lower ends of the angle irons 46. Holes 90 in the retarding pad and openings 91 in the plate 84 clear the studs.

Because of the inherent damping in the driving pad, the retarding pad 86 need not absorb as much force as is required to be absorbed by the driving pad 60. Consequently, I make the retarding pad 86 materially thinner than the pad 60. The retarding pad may be made of a stack of discs similar to the discs 62, 64, 66. In some instances I may use two thick plain discs 92 similar to 62, as shown in FIG. 7. I may include one or more corrugated discs similar to the corrugated discs 66, or as shown in FIGS. 1 and 8, I may use four thin plain discs 94 corresponding to the discs 64.

Preferably both the driving pad and the retarding pad are preloaded axially in compression. When the mandrel is assembled the thickness of each of the stacks constituting the pads is greater than the space provided for them between the foot plate 14 and the guts plate 84 and between the head plate 12 and the guts plate 80. When the head plate 12 is bolted against the end of the tube 10 as shown in FIG. 1, this compresses both pads and preloads them axially. The amount of preloading in each of the driving and retarding pads varies with the requirements of the particular use of a particular mandrel and is influenced by the length of the mandrel, the weight and flexibility of the guts, and the amount of clearance between the guts and the wall of the tube. The amount of preloading is selected so that when the greatest acceleration occurs in a given mandrel the force to inertia of the guts is instantly opposed by a sufficient driving force in the driving pad to accelerate the guts smoothly without objectionable vibration and hammering on the pad. The desired value of the preload is achieved by selection of the kind and number of discs.

Regardless of how smooth I make the lower surface of the lower guts plate 84, and regardless of the minimum practical clearance between the edge of this plate and the walls of the tube 10, I find that a resilient retarding pad, made as described above, is soon destroyed. I believe this is caused partly by the twisting of the guts under the influence of the screwing action of the spirally corrugated shell and partly by lateral motion due to bending of the guts, so that the end plate moves back and forth over the surface of the pad as much as is permitted by the necessary clearance between the pins 88 and the holes 91 in the end plate 84 and by the clearance between the edge of the plate 84 and the inner wall of the tube. Although the movement is small the axial force between the end plate and the pad is very large, and small movement under this large force can be destructive.

I have found that I can prevent this destruction and make a long lasting pad by placing between the end plate 84 and the retarding pad 86 a layer 96 of tough, flexible, very slipper material. I have found molded nylon to be suitable for this purpose. If desired a similar nylon pad can be used between the pad 60 and the plate but in practice I have found this not to be necessary. I do not clearly understand the reasons for this.

If the mandrel tube 10 were always to be used alone without being joined to another mandrel the foot plate 14 could be joined to the tube 10 by bolts as is head plate 12, and this would be the bottom surface of the mandrel which punches the hole in the earth. For many reasons it is desirable to have the mandrel as short as possible to drive a pile of the required length. It is impractical ala ways to have a mandrel as long as the longest pile to be driven, such as 80 feet, and to be required to use this for 8 driving short piles such as twenty or forty feet. Consequently I provide means for joining two mandrels together so that I can use, for example two forty foot man- A drels to drive eighty feet of casing, or I can use a ten foot mandrel joined to a forty foot mandrel to drive a fifty foot casing.

The lower or bottom is generally similar to the upper mandrel but it may be different in details of construction. As shown in FIG. 8, a lower tube has a head plate 112 welded to its upper end and a foot plate 114 bolted to its lower end, which forms the surface which punches the hole into the earth. The head plate 112 has a coupling sleeve 16' welded to it which is a duplicate of the coupling sleeve 16 welded to the lower end of the upper tube 10. The coupling sleeves 16, 16' receive the opposite cylindrical ends 202 of the coupling 18, previously i referred to, and the ends of the sleeves abut a collar 204 integrally joined to the ends 202 which transmits the driving force from the upper mandrel to the lower mandrel. The mandrels are held against separation by the coupler 18 which locks them together by two sets of keys in the form of balls 206 placed in mating grooves 208 (in each sleeve 16, see FIG. 1) and 210 (in each cylindrical end 202). When the mandrels are assembled in alignment with the ends of the coupling sleeves 16 firmly abutted against the collar 204, the grooves 210 register with the grooves 208 to form a closed chamber into which the balls 206 are inserted through openings 212. The openings are later closed by plugs 214.

The lower mandrel has the same slots 20, plugs 22, rails 26, springs 36, and hoses 42 that the upper mandrel has. It has similar guts including a central square tube 144,

corresponding to the tube 44, which supports the hoses I and is welded to angle irons 146 corresponding to the angle irons 46. The ends of this have a top end plate and a bottom end plate 184. A manifold 148 for supplying the hoses 46 through hose connections 52 is It is necessary to conduct air pressure from the upper mandrel to the hoses in the lower mandrel 110. To provide for this the upper square tube 44 has at its lower end the rounded section 56, previously referred to, and the lower square tube 144 has inside its upper end a round conduit section 216 having a shoulder forming a stop for a connecting tube 220 having O-ring seals 222. The tube extends from the lower mandrel through the coupler 18 into the upper mandrel, having a sliding, sealing fit with the round section 56 of the square tube 44. When the mandrels are to be connected, the tubes 10 and 110 are horizontal and aligned. The coupler is secured to one, for example the bottom mandrel and the connecting tube 220 is inserted into the tube 216 against the stop 218. The connecting tube is long enough to reach into the upper mandrel while the mandrels are separated, and forms a sliding seal with the round tube 56. Then the upper mandrel tube 10 is moved up to the lower mandrel tube and fastened to the coupler 18. The O-rings provide a sliding seal Within the tubes 56 and 216 and maintain a sealed connection between the two mandrel sections by establishing a pneumatic connection between the square tubes 44 and 144, When the upper mandrel is to be used alone there is no pressure in the upper square 44 because access to the tube is prevented by a plug 230 shown in FIGS. 1 and 5, previously referred to. However when the two mandrels are to be joined the plug 230 is removed through the interior of the connection 50. This supplies the lower hoses with air pressure whenever air pressure is supplied to the upper hoses. The lower hoses are sealed as are the upper hoses by having their ends pinched together, cemented, and clamped around a round section 156 corresponding to the section 56 and forming the lower end of the square tube 144. The lower end of the square tube 144 is sealed to maintain air pressure therein by a plug 232 having O-ring seals 234 and held in place by the lower retarding pad 186 which differs from the upper retarding pad 86 by being irnperforate at its center. However the lower pad is perforated at its edges to receive studs corresponding to studs 88 in FIG. 1 to prevent relative rotation of the tube 110 and the lower end of the guts. Such studs do not appear in the section shown in FIG. 8.

Example In one successful embodiment of the invention a single unjointed mandrel was 60 feet long, 11 inches outside diameter and 8 /2 inches inside diameter. The driving pad 60 consisted of a stack of five plain discs 62 approximately one-half inch thick, six plain discs 64 approximately inch thick, and seven corrugated discs 66 about inch thick, assembled as shown in FIG. 3. The corrugations occupied approximately & inch of the thickness of each disc for a total of Z of an inch of corrugations for the entire stack. Each disc was a stack of layers of textile fabric at the rate of about 60 layers of fabric per inch of thickness of the disc. The layers of fabric were impregnated and bonded by a cured elastomer of the nature of synthetic rubber. The discs are known in the trade as Fabreeka, and are sold by Fabreeka Products Co., Boston, Massachusetts. The total unstressed axial thickness of the driving pad assembled as described was 4 inches. The retarding pad 86 consisted 'of two plain discs 90 each approximately /2 inch thick made as described above. It was accompanied by a nylon layer 96 approximately A; inch thick. The unstressed axial length of the retarding pad and nylon pad together was 1% inches. All discs were 8% inches in diameter. The discs of the driving pad had central holes approximately 4 inches square and the discs of the retarding pad had a central hole 2 inches in diameter and four stud holes each 1% inches in diameter.

When 'the mandrel was assembled and all parts in place except for head plate 12, the driving pad 60 projected approximately- A of an inch above the top of the tube 10. A force of approximately 5950 pounds was required to compress all the pads until the head plate 12 lay snuggly against the top of the tube 10 whereupon it was bolted in place.

It was found that the one inch of Fabreeka pads at the bottom of the mandrel was compressed approximately & of an inch, that the guts was shortened approximately 19, of an inch and that the driving pad was compressed approximately of an inch. The guts was shortened according to the formula PL/AE, where P is the applied load in pounds, L is the length of the guts, A is the cross sectional area of the steel in the guts and E is the modulus of elasticity of that steel. Under the load of 5950 pounds the elongation of the large tube 10 was too small to be measured, due to its large cross sectional area and the modulus of elasticity of the steel of which it was made.

FIG. 10 is an observed compression-loading curve of the driving pad itself, constructed and assembled as described above. It will be noted that the force of ap-. proximately 5950 pounds compression load reduces the thickness of this particular stack of an inch, which agrees with the results observed in a mandrel assembly.

It is to be understood that the structure illustrated and described, and the language used in the description are illustrative only, and do not constitute any limitation of the invention.

I claim:

1. A mandrel for driving spirally corrugated pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a coupling sleeve secured to the other end of the tube for receiving a device for coupling a second tube to the first mentioned tube, a foot plate secured to the other end of the first mentioned tube for transmitting driving force to the sleeve, a plurality of shell-driving plugs distributed along the length of the tube which are expressible from the tube to engage the spiral corrugations of a surrounding pile shell, means for retracting the plugs within the outer surface of the tube, means disposed along the length of the tube for expressing the plugs, a torslonally flexible floating support for the expressing means including a group of elongated bar-s extending substantially the length of the tube between the plates, a transverse plate secured to each end of the group of bars, said support and expressing means being contained within the tube between the head and foot plates, an axial principal stack of perforated elastomeric driving pads preloaded in compression axially of the tube disposed between the head plate and the transverse plate on the adjacent end of the support, said stack comprising alternate relatively thick and relatively thin pads of textile fabric, each pad being impregnated and bonded with elastomer, some of the thin pads having on one surface a corrugated layer of impregnated fabric forming a plurality of parallel springs, the directions of the corrugations of alternate corrugated pads being disposed transverse to one another and such alternate corrugated pads being separated by flat, noncorru-gated pads.

2. A mandrel for driving spirally corrugated circular shells into the earth, comprising in combination an elongated circular tube, a driving head plate attached to one end of the tube for transmitting driving force between the plate and the tube under the impact of a driving hammer, a coupling sleeve secured to the other end of the tube for receiving a device for coupling a second tube to the first mentioned tube, a transverse plate secured to said other end of the tube for transmitting driving force to said sleeve, a plurality of shell-driving members distributed along the length of the tube and expressible from the tube to engage the spiral corrugations of a she-ll, means for retracting the driving members within the outer surface of the tube, means disposed along the length of the tube for expressing the driving members, a floating support for the expressing means extending substana,2ss,5 19

tially the length of the tube between the plates, said support including a fluid pressure chamber extending substantially the length of the tube, said support and expressing means being contained between said plates and within the first mentioned tube without being rigidly attached to the tube or either plate, an opening in the second mentioned plate for receiving a conduit for conducting fluid pressure from the fluid pressure chamber to a second tube and means between the opening and the wall of the tube relatively movable axially with respect to the support for limiting relative rotation between the tube and the adjacent end of the support.

3. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube,a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a torsionally flexible floating support for the expressing means extending substantially the length of the tube bewteen the plates, said support and expressing means being contained within the tube between the plates, a resilient driving member between the head plate and one end of the support, a resilient retarding member between the foot plate and the other end of the support, and means connected to the foot plate and extending through the retarding member, said last-named means slidably engag ing the adjacent end of the support and establishing a non-rotative connection between the foot plate and the adjacent end of the support.

4. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a torsionally flexible floating support for the expressing means extending substantially the length of the tube between the plates, said support and expressing means being contained within the tube between the plates, a resilient driving member between the head plate and one end of the support, a perforate elastomeric retarding pad between the foot plate and the other end of the support, and rod means secured to the foot plate, said rod means being disposed eccentrically of the longitudinal axis of said support and extending through the perforations of said pad and engaging the support to prevent relative rotation between the adjacent end of the support and the foot plate.

5. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a floating support for the expressing means extending substantially the length of the tube between the plates, said support and expressing means being contained within the tube between the plates, said support presenting a smooth surface at one end extending radially of the tube, and an elastomeric force transmitting pad between the head plate and one of said radially extending surfaces, an elastomeric retarding pad between the foot plate and the other radially extending surface and a flexible, smooth, slippery layer between one of said pads and said other radially extending surface.

6. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a floating support for the expressing means extending substantially the length of the tube between the plates, said support and expressing means being contained within the tube between the plates, said support presenting a surface at each end extending radially of the tube, and an elastomeric force transmitting pad engaged under compression between the head plate and one of said radially extending surfaces, and an elastomeric retarding pad engaged under compression between the foot plate and the other radially extending surface.

7. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a floating support for the expressing means extending substantially the length of the tube between the plates, said support and expressing means being contained within the tube between the plates, an elastomeric driving pad engaged under compression between the head plate and one end of said support, and an elastomeric retarding pad engaged under compression between the foot plate and the other end of the support, the driving pad being materially thicker than the retarding pad.

8. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a floating support for the expressing means extending substantially the length of the tube between the plates, said support and expressing means being contained within the tube between the plates, a resilient driving member preloaded in compression axially of the tube between the head plate and one end of the support, and a resilient retarding member preloaded in compression axially of the tube between the foot plate and the other end of the support, the driving member having greater resist ance to compression loading axially of the tube than the retarding member.

9. A mandrel for driving pile shells into the earth com prising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means Within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a floating support for the expressing means extending substantially the length of the tube between the plates, said support and expressing means being con- 1 1 tained within the tube between the plates, a resilient driving member preloaded in compression axially of the tube between the head plate and one end of the support, and a resilient retarding member preloaded in compression axially of the tube between the foot plate and the other end of the support.

10. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving con necting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means Within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a floating support for the expressing means extending substantially the length of the tube between the plates, said support and expressing means being contained within the tube between the plates, and damped resilient force transmitting means engaged under compression in the axial direction of the tube and between each of said plates and the adjacent end of the support.

11. A mandrel for driving pile shells into the earth comprising in combination an elongated tube, a head plate secured to one end of the tube for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the tube, a plurality of shell-driving connecting means distributed along the length of the tube which are expressible from the tube to engage a surrounding pile shell, means for retracting the connecting means within the outer surface of the tube, means disposed along the length of the tube for expressing the connecting means, a floating support for the expressing means extending substantially the length ofthe tube between the plates, said support and expressing means being contained within the tube between the plates, and resilient force transmitting means preloaded in compression axially of the tube between one of said plates and the adjacent end of the support.

12. A mandrel for driving pile shells into the earth comprising in combination an elongated rigid member, a head plate secured to one end of the member for transmitting force of a driving hammer to the tube, a foot plate secured to the other end of the member, a plurality of shell-driving connecting means disposed along the length of the member which are expressible from the member to engage a surrounding pile shell, means for retracting the connecting means from engagement with the pile shell, means disposed along the length of the member for expressing the connecting means, a floating support for the expressing means extending lengthwise of the member between the plates, and an elastomeric force transmitting pad engaged under compression between each of said plates and the adjacent end of the support.

13. Apparatus as defined in claim 12 in which the elastomeric pads each comprise a stack of alternating, relatively thick and relatively thin, centrally perforated discrete discs, each disc being a laminated stack of layers of textile fabric impregnated and bonded with an elastomer.

14. Apparatus as defined in claim 12 in which the clastomeric pads each comprise a stack of centrally perforated discrete discs, each disc being a laminated stack of layers of textile farbic impregnated and bonded with an elastomer.

15. Apparatus as defined in claim 12 in which the clastomeric pads each comprise a stack of relatively thick and relatively thin, discrete discs, each disc being a laminated stack of layers of textile fabric impregnated and bonded with an elastomer.

16. Apparatus as defined in claim 12 in which the elastomeric pads each comprise a stack of alternating, relatively thick and relatively thin discrete discs, each disc being a laminated stack of layers of textile fabric impregnated and bonded with an elastomer.

17. Apparatus as defined in claim 12 in which the elast-omeric pads each comprising a stack of discrete discs, each disc being a laminated stack of layers of textile fabric impregnated and bonded with an elastomer.

18. Apparatus as defined in claim 12 in which the elastomeric pads each include a stack of discrete discs having a plurality of such discrete discs formed with corrugations providing axially defiectable parallel springs, alternate corrugated discs having their corrugations transverse to one another, and separated by a flat, noncorrugated disc.

19. Apparatus as defined in claim 12 in which the elastomeric pads each include a stack of discrete discs having a plurality of such discrete discs formed with corrugations providing axially deflectable parallel springs, alternate corrugated discs having their corrugations transverse to one another.

20. Apparatus as defined in claim 12 in which the elastomeric pads each include a stack of discrete discs having a plurality of such discrete discs formed with corrugations providing axially deflectable parallel springs.

References Cited by the Examiner UNITED STATES PATENTS 2,684,577 7/1954 Smith 6l53.72 2,869,329 1/1959 Jourdain 6153.72 2,972,872 2/1961 Kupka 6l53.52 3,006,152 10/1961 Rusche 6l--53.72 3,068,131 12./1962 Morton 161-42 3,130,110 4/1964 Schmidt 16142 3,190,078 6/1965 Rusche 6153.72

CHARLES E. OCONNELL, Primary Examiner.

JACOB SHAPIRO, Examiner. 

1. A MANDREL FOR DRIVING SPIRALLY CORRUGATED PILE SHELLS INTO THE EARTH COMPRISING IN COMBINATION AN ELONGATED TUBE, A HEAD PLATE SECURED TO ONE END OF THE TUBE FOR TRANSMITTING FORCE OF A DRIVING HAMMER TO THE TUBE, A COUPLING SLEEVE SECURED TO THE OTHER END OF THE TUBE FOR RECEIVING A DEVICE FOR COUPLING A SECOND TUBE TO THE FIRST MENTIONED TUBE, A FOOT PLATE SECURED TO THE OTHER END OF THE FIRST MENTIONED TUBE FOR TRANSMITTING DRIVING FORCE TO THE SLEEVE, A PLURALITY OF SHELL-DRIVING PLUGS DISTRIBUTED ALONG THE LENGTH OF THE TUBE WHICH ARE EXPRESSIBLE FROM THE TUBE TO ENGAGE THE SPIRAL CORRUGATIONS OF A SURROUNDING PILE SHELL, MEANS FOR RETRACTING THE PLUGS WITHIN THE OUTER SURFACE OF THE TUBE, MEANS DISPOSED ALONG THE LENGTH OF THE TUBE FOR EXPRESSING THE PLUGS, A TORSIONALLY FLEXIBLE FLOATING SUPPORTING FOR THE EXPRESSING MEANS INCLUDING A GROUP OF ELONGATED BARS EXTENDING SUBSTANTIALLY THE LENGTH OF THE TUBE BETWEEN THE PLATES, A TRANSVERSE PLATE SECURED TO EACH END OF THE GROUP OF BARS, SAID SUPPORT AN EXPRESSING MEANS BEING CONTAINED WITHIN THE TUBE BETWEEN THE HEAD AND FOOT PLATES, AND AXIAL PRINCIPAL STACK OF PERFORATED ELASTOMERIC DRIVING PADS PRELOADED IN COMPRESSION AXIALLY OF THE TUBE DISPOSED BETWEEN THE HEAD PLATE AND THE TRANSVERSE PLATE ON THE ADJACNET END OF THE SUPPORT, SAID STACK COMPRISING ALTERNATE RELATIVELY THICH AND RELATIVELY THIN PADS OF TEXTILE FABRIC, EACH PAD BEING IMPREGNATED AND BONDED WITH ELASTOMERR, SOME OF THE THIN PADS HAVING ON ONE SURFACE A CORRUGATED LAYER OF IMPREGNATED FABRIC FORMING A PLURALITY OF PARALLEL SPRINGS, THE DIRECTIONS OF THE CORRUGATIONS OF ALTERNATE CORRUGATED PADS BEING DISPOSED TRANSVERSE TO ONE ANOTHER AND SUCH ALTERNATE CORRUGATED PADS BEING SEPARATED BY FLAT, NONCORRUGATED PADS. 